Although applicable to any devices for optical parallel analysis of a sample arrangement, the exemplary embodiments and/or exemplary methods of the present invention and the problem on which it is based are explained with regard to utilization in microtiter plates.
For optical analyses of individual biochemical samples, microtiter plates or DNA chips are frequently used, on which the objects of analysis are provided, spatially separated from each other in discrete sample areas. Faster results are achieved through parallel performance of the optical analysis on a large number of individual samples than with sequential performance of individual analyses. Moreover, miniaturization of the individual batches results in a saving of reagent.
Microtiter plates are usually rectangular, and contain as sample areas many mutually isolated miniature cups in rows and columns for testing biological properties and reactions, for example through measurements of absorption, fluorescence and luminescence, for example for so-called high-throughput screening (HTS), in pharmaceutical and plant protection research. In most cases the plates are made of plastic, normally polystyrols, sometimes also polyvinyl chloride, but for very special applications also glass. The exact dimensions, according to the ANSI standard, are 127.76 mm×85.48 mm×14.35 mm. There are a multitude of formats, all on the same base area and in some cases having variable height, there normally being between 6 and 1536 miniature cups present. The miniature cups are available in various shapes, for example as flat bottoms, as flat bottoms with minimally rounded corners, as conically tapering bottoms, as U-shaped depressions.
Because of the small sample quantity required and the possibility of automation, microtiter plates have gained acceptance as an important element for research in the areas of pharmaceutics, medicine, biochemistry, genetics and molecular biology.
An optical system having a lens array and a field lens which depicts an object array on a detector array is discussed in DE 197 48 211 A1.
A device is discussed in DE 100 17 824 A1 for parallel photometric fluorescence or luminescence analysis of a plurality of mutually separated sample areas on an object.
FIG. 4 is a schematic depiction of a known device for optical parallel analysis of a sample arrangement in the form of a microtiter plate.
In FIG. 4, reference numeral 1 designates a carrier substrate 1 of plastic in the form of a microtiter plate. In front face VS of carrier substrate 1 an arrangement of sample areas K1, K2 is provided for receiving a sample substance A1, A2. Sample areas K1, K2 are cavities which have been formed, bored or milled into carrier substrate 1.
Placed on back face RS of carrier substrate 1 are detector areas D1, D2, which are each assigned to a corresponding sample area K1, K2. Thus each sample area K1, K2 with the associated detector area D1, D2 takes up essentially the same space, which is indicated by a virtual dividing line T.
If the sample substances are irradiated from front face VS of carrier plate 1 with excitation radiation AS in the course of an optical parallel analysis, then emissions occur in sample substance A1, A2, which involve beams MS1, MS2 and ST, for example light beams. Beams MS1 and MS2 are directed at detector areas D1 and D2, which are assigned to sample areas K1 and K2, with sample substance A1 and A2. These beams MS1, MS2 are thus regular measuring signals.
Light beam ST passes from sample substance A2 to detector area D1, which is assigned to sample area K1 with sample substance A1. In this respect, light beam ST is an interfering beam and lowers the signal-to-noise ratio of sample area K1. In other words, beam ST forms an optical contamination of the measuring signal of detector area D1, since it is stray light from adjacent sample area K2.